The disclosure of the following priority application is herein incorporated by reference:
Japanese Patent Application No. 2000-155496, filed May 25, 2000.
1. Field of the Invention
The present invention relates to a shape measurement device for an article whose shape is required to be accurate, and in particular relates to a shape measurement device intended for the measurement of a carrier which is used upon a semiconductor device production line for transporting a set of several semiconductor wafers all together.
2. Description of the Related Art
Upon a production line for semiconductor devices, in order to transport a semiconductor wafer between devices which perform film deposition, processing or the like, there has been employed a per se known method of transporting the semiconductor wafers by collecting together several at one time in a receptacle termed a xe2x80x9ccarrierxe2x80x9d. Generally, this type of carrier is formed with a number of slots being provided upon its inner walls on both its sides at predetermined intervals, and is made so as to hold a plurality of semiconductor wafers in a horizontally superimposed state with predetermined intervals between them, by supporting both the sides of the semiconductor wafers by these grooves.
When a semiconductor wafer is to be taken out from the carrier after it has been transported and is to be inserted into a device which performs a process like film deposition, processing or the like, a so called xe2x80x9crobot armxe2x80x9d device inserts the end of an arm, which is formed in a thin plate shape, between two adjacent semiconductor wafers in the carrier. Then the end of the robot arm performs the operation of pulling a single semiconductor wafer out forwards towards itself along the grooves while lifting it up by its under surface.
At this time there is a danger that, if the space between one semiconductor wafer and the adjacent one supported in the carrier deviates from its design value by more than its permitted value, the end of the robot arm may touch against the upper surface of the adjacent semiconductor wafer. Since film deposition, processing or the like has been performed upon the upper surfaces of the semiconductor wafers by the previous processes up until this point, it is not desirable for the end of the robot arm to come into contact with any upper wafer surface, because damage or contamination may result. Furthermore, if the heights at which the semiconductor wafers are supported in the carrier deviate from the design values, apart from the possibility that the robot arm may touch the upper surface of some semiconductor wafer, there is a danger that one semiconductor wafer may be damaged by collision with the front edge of the semiconductor wafer. Yet further, if one of the semiconductor wafers is tilted, the end of the robot arm may not be able properly to lift up this semiconductor wafer. Due to these problems, it is extremely important for the heights at which the semiconductor wafers are supported in the carrier, the spaces between the semiconductor wafers, and the inclinations of the semiconductor wafers, all to be constrained to be within their permitted ranges around their design values.
For this reason, a shape measurement operation is performed at the time of shipping of the carrier from the carrier manufacturer and/or at the time of receipt of the carrier by the semiconductor device maker, in order to determine whether or not the shape of the carrier accords with its design values. Further, it may happen that the carrier becomes deformed during use, since cleansing processes and the like upon a semiconductor device production line are performed at high temperatures. Due to this, a measurement operation may be performed by the semiconductor device maker while the carrier is partway along the production line, in order to check whether or not its shape accords with its design values.
There is a per se known prior art carrier shape measurement device which measures the shape of a so called open carrier in which apertures are formed both in its front surface and also in its rear surface. With this structure, this open carrier is illuminated from its rear, and images are formed by a CCD camera or the like of the external shape of the carrier and the shapes of the grooves from the front, and the process of shape measurement is performed by processing these images.
However, since the grooves in the carrier are formed upon both the sides thereof, even if the shapes of these grooves are measured, it has been difficult accurately to derive from these values the spaces between the central portions of the wafers which are supported in these grooves, and their heights and inclinations. In particular, with a carrier shape measurement device according to this prior art, since the images which are used are formed from the front side of the carrier, therefore information cannot be obtained as to what the shapes of the grooves may be, further in the direction into the grooves than the depth of focus of the CCD camera. Because of this, even though the spaces between the wafers which are supported in these grooves, and their heights and inclinations, can be derived with accuracies on the order of millimeters, there have been great difficulties in increasing the accuracy above such a level.
More particularly, in recent years, the use has increased of so called large size semiconductor wafers of diameter of 300 mm or greater. Since both the edges of these large size semiconductor wafers are supported in the carrier in grooves which are several millimeters deep, it becomes more and more difficult to know, from the shapes of the grooves, the state of support with regard to the spaces between the central portions of the wafers and their inclinations and the like. Moreover since, in the case of semiconductor wafers of large diameter, if a wafer is inclined even a little, the spaces between it and the neighboring wafers become extremely restricted, therefore a measurement accuracy on the order of millimeters is no longer adequate, and a further enhancement of the accuracy of measurement is desirable.
Yet further, since such a carrier measurement device according to the prior art is directed towards measurement of an open carrier, therefore it is not capable of being applied to the measurement of the shape of a sealed type carrier which has a blocked rear side and a cover over its front side, such as a so-called FOUP (Front Opening Unified Pod) carrier for wafers of 300 mm diameter according to the SEMI standard.
The objective of the present invention is to propose a carrier shape measurement device which can measure with high accuracy the shape of a carrier and the attitudes of semiconductor wafers which are loaded into the carrier.
In order to attain the above described objective, a carrier shape measurement device according to the present invention, comprises: a stage which supports a carrier which is to be a subject of measurement; and a measurement section which measures a shape of the carrier, and the stage comprises kinematic coupling pins to support the carrier by a kinematic coupling.
In this carrier shape measurement device, it is preferred that the stage comprises a surface which coincides with or is parallel to at least one of a horizontal datum plane, a facial datum plane, and a bilateral datum plane which are specified with respect to the carrier which is supported by the kinematic coupling. In this case, it is preferred that the measurement section measures the shape of the carrier by taking as a reference the coinciding or parallel surface of the stage. Furthermore, it is preferred that a shifting section which shifts the measurement section relatively to the carrier is provided, and a direction of shifting by the shifting section is parallel or perpendicular to the coinciding or parallel surface of the stage.
In the above carrier shape measurement device, it is preferred that a calculation section which calculates results of measurement by the measurement section is further provided, and the calculation section derives coordinates of a center of a wafer which is loaded into the carrier by substituting coordinates of a plurality of points upon an edge of the wafer which have been measured by the measurement section, into a predetermined equation.
In the above carrier shape measurement device, it is preferred that the stage comprises a mechanism section which vibrates the kinematic coupling pins.
In the above carrier shape measurement device, it is preferred that a detection section which detects whether or not an engagement between the carrier and the kinematic coupling pins is normal, and a control section which, if the detection section has detected that the engagement is normal, stops vibrating by the mechanism section, are further provided.
In the above carrier shape measurement device, it is preferred that each of the kinematic coupling pins comprises an air ejection orifice for ejecting air from its tip towards the carrier, and a flow conduit which conducts air to the air ejection orifice. In this case, it is preferred that a detection section which detects whether or not an engagement between the carrier and the kinematic coupling pins is normal, and a control section which, if the detection section has detected that the engagement is normal, stops supplying air to the flow conduit, are further provided.
In the above carrier shape measurement device, it is preferred that the kinematic coupling pins comprise three pins arranged in a predetermined arrangement, and in order to support the carrier in a desired orientation with the kinematic coupling pins, the stage is made with such a structure that an orientation of the arrangement of the three pins upon the stage can be changed while the arrangement is being maintained relatively between the three pins. In this case, it is preferred that the stage comprises a plate which comprises the kinematic coupling pins, and a support portion upon which the plate is loaded; and the support portion comprises a mechanism which can change a loading direction of the plate, in order to change the orientation of the arrangement of the three pins. Furthermore, it is preferred that a dimension calculation section which calculates dimensions of the carrier from results of measurement by the measurement section is further provided, and the dimension calculation section calculates the dimensions of the carrier either by using coordinates which result from the measurements just as they are, or by using coordinates which have been converted by the coordinate conversion section. Also, it is preferred that the stage comprises a plate which comprises the kinematic coupling pins, and a rotation section which rotates the plate. Also, it is preferred that the stage comprises a plurality of kinematic coupling pins whose arrangements of the three pins differ from one another, a mechanism section for projecting and retracting the plurality of kinematic coupling pins from the stage, and a control section which controls the mechanism section so as selectively to project one of the plurality of kinematic coupling pins from the stage. Also, it is preferred that a coordinate conversion section which converts coordinates of results of measurement according to the orientation of the kinematic coupling pins upon the stage, is further provided.
In the above carrier shape measurement device, it is preferred that a calculation section which calculates results of measurement by the measurement section is further provided, and the calculation section derives coordinates of a center of a wafer which is loaded into the carrier by adding a dead weight bending amount, which has been determined in advance from a weight of the wafer, to at least one of coordinates of a wafer support portion of the carrier which have been measured by the measurement section, and coordinates of a point upon an edge of the wafer which have been measured by the measurement section.
In the above carrier shape measurement device, it is preferred that a calculation section which calculates results of measurement by the measurement section is further provided, and the calculation section, by using coordinates of left and right wafer support portions of the carrier which have been measured by the measurement section, derives an inclination of a wafer which is loaded into the carrier and which is supported by the wafer support portions.
In the above carrier shape measurement device, it is preferred that the stage comprises a surface which coincides with or is parallel to a surface based upon a designed shape of the carrier.
In the above carrier shape measurement device, it is preferred that the measurement section measures a shape of the carrier by comparison with the coinciding or parallel surface of the stage.
Another carrier shape measurement device comprises: a stage which supports a carrier which is to be a subject for measurement; an imaging section which forms an image of the carrier; and a calculation section which calculates image formation results of the imaging section, and the imaging section comprises an objective lens, and an operational distance of the objective lens is longer than a distance from an opening of an aperture for taking a wafer out from the carrier and inserting it thereinto, to a wafer support portion within the carrier.